Field
The disclosed and claimed concept relates generally to electrical distribution equipment and, more particularly, to a method of operating an electrical feeder to enable improved implementation of conservation voltage reduction thereon.
Related Art
Numerous types of electrical generation and distribution equipment are known in the relevant art. For instance, electricity is purchased by electrical utilities from distant electricity generation entities and is transmitted via high tension lines to intermediate distribution centers such as substations and the like. The electrical power is sent from a substation, for instance, along an electrical conductor known as an electrical feeder, and the electrical power is provided to various loads and other devices that are electrically connected with the electrical feeder.
As is generally understood, electrical power can be said to include real power and reactive power. A purely resistive load such as an electrical resistance wire typically consumes only real power. Other electrical loads such as electric motors or other devices may include inductive load components or capacitive load components or both, and such electrical loads may be said to consume both real power and reactive power.
Since the electrical feeder has numerous types of loads situated at various locations along its length, and the impedance (including both real/active power and reactive components) of the feeder conductor causes voltage drop, the voltage of the real power can vary widely at the various locations along the electrical feeder, as can the availability of reactive power, which is measured in units of var. In order to control the voltage and other aspects of the electrical power on the electrical feeder, the electrical feeder typically has connected therewith a number of voltage control devices that are operable to control the voltage and potentially other aspects of the electrical power on the electrical feeder and can include numerous types of devices. As employed herein, the expression “a number of” and variations thereof shall refer broadly to any non-zero quantity, including a quantity of one. One such device is a voltage regulator, and other such devices include capacitor banks, load tap changers (LTC devices, which perform like a variable transformer), devices such as certain series capacitors, controllable inverters/converters connecting the feeder with energy storage, renewable generators (wind, solar, etc.), or similar source and loads. Such voltage control devices can control the voltage of the electrical power on the electrical feeder and potentially also have the capability to affect the reactive power that is available on the electrical feeder.
The electrical feeder additionally typically has a number of sensors situated thereon or otherwise associated therewith at various locations along its length that provide data via telemetry or via other communication technology to the substation or centralized control center. The substation/control center typically includes a control mechanism that controls the various voltage control devices based upon signals received from the various sensors that are on the electrical feeder and based upon other input. The sensors might provide to the substation data concerning the magnitude and phase angle of both the voltage and the current at that location on the electrical feeder. The control system that is situated at the substation and that controls the various voltage control devices is typically a computerized system that is included in a Distribution Management System (DMS) or a separate system performing similar functions. A DMS normally has a dynamic state engine application deployed and operating thereon. The dynamic state engine detects the various data from the various sensors and provides instructions to the various voltage control devices to adjust the voltage to be at an appropriate level on the electrical feeder.
By way of example, typical domestic electrical power delivery in the United States may be at a nominal value of 120 volts AC at the feeder end, but the voltage is permitted to vary between 114 volts and 126 volts. If a utility employs conservation voltage reduction (CVR), it typically will provide electricity at a voltage that is in the lower end of the acceptable voltage range. Such CVR methodologies are able to reduce the consumption of electrical power by pure resistive loads and by the resistive components of other types of loads. While the provider of electrical power is permitted to maintain the voltage as low as 114 volts in the present example, the provider typically would not operate its electrical feeder at the minimum acceptable voltage since a sudden increase in the electrical load or a sudden drop in distributed electrical generation on the electrical feeder potentially could drive its voltage, at least momentarily, below the acceptable minimum voltage level. As such, CVR is typically implemented at a voltage higher than the minimum voltage in order to provide a buffer zone above the minimum voltage in order to ensure that the voltage never drops below the minimum acceptable voltage. While such systems have been generally effective for their intended purposes, they have not been without limitation.
In recent years, distributed generators such as photovoltaic arrays and wind turbines/farms and the like have become prevalent and are typically connected with electrical feeders. Such distributed generators are generators of electrical power, i.e., electrical generators, and they are known by any of a variety of terms in the relevant art and generate electrical power that is supplied, at least in part, to the electrical feeder to which they are connected. Some of the electrical power that is being generated by the distributed generators may additionally be consumed by a closely related load, such as when a homeowner may install a number of solar panels on the rooftop in order to help generate some of the electricity that is needed in the household. At certain times, all of the electricity that is being generated by such distributed generators might be consumed by closely associated loads, and at other times excess power that is being generated by the distributed generators but that is not being consumed by the closely associated loads is being delivered to the electrical feeder. In the latter situation, the homeowner receives a credit for the electrical power that is supplied to the electrical feeder.
While such distributed generators have been generally desirable to society as a whole, they introduce certain difficulties into the management of electrical feeders because, by their nature, the amount of electrical power that is generated and that is supplied to the electrical feeder can vary. For instance, photovoltaic arrays typically generate electricity at most only during the daytime, and even then the rate at which power is generated depends upon the irradiations level/location of the sun and whether clouds are situated between the sun and the solar panels. Power production with such photovoltaic arrays can vary widely and rapidly on otherwise clear days having separated clouds floating in the sky. With wind generation, the power can vary with the extent to which wind is impinging on the impeller at any given moment. As such, difficulty has be encountered in maintaining the electrical feeder voltage at a given level due to the variable injection of electrical power into the electrical feeder by such distributed generators. Also, difficulty has been encountered in determining whether or not voltage control devices are operating properly since the voltage can be affected by whether or not the distributed generators are supplying electrical power to the electrical feeder. Inasmuch as the addition of such distributed generation devices has increased the complexity of managing an electrical feeder, improvements would be desirable.